Liquid fuel controlling means for jet-engines, gas turbines, or like prime movers



July v13, 1954 Y T A HARRIS 2,683,485

.. LIQUID FUEL CONTROLLING MEANS FOR JET-ENGINES, GAS

l TURBINES, OR LIKE PRIME MOVERS Filed Deo. l1. 1950 lin/U czzo PatentedJuly 13, `1954 LIQUID FUEL CONTROLLING MEANS FOR JET-ENGINES, GASTURBINES, OR LIKE PRIME MOVERS Thomas Alfred Harris, Edgbaston,Birmingham, England, assignor to Joseph Lucas Limited, Birmingham,England Application December 11,v 1950, Serial No. 200,278

Claims priority, application Great Britain December 19, 1949 Thisinvention relates to the liquid fuel controlling means employed on jetengines, gas turbines or like prime movers, of the kind which include aliquid-operated servo-mechanism for automatically varying the rate ofsupply of fuel to the combustion chamber or chambers, and also a controlmeans operable b-y the driver.

In some such systems it is possible to obtain a temporary butundesirable excess of fuel supply to the combustion chamber when thethrottle is opened suddenly, and the object of the present invention isto obviate this condition.

I'he invention comprises the combination with a valve for controllingthe servo-mechanism, of valve actuating means responsive to a pressuredifference set up in the system in response to a change of pressureaccompanying a change in the rate of flow of the liquid fuel, the saidmeans including a piston slidable in a cylinder and loaded by a springwhich at one end is supported by one side of a valve-actuating lever,and a diaphragm (or piston) of smaller effective diameter acting on theopposite side of the lever, the first mentioned piston and the diaphragm(or piston) being responsive to the said pressure difference.

The accompanying diagram illustrates one mode of carrying the inventioninto effect.

Referring to the diagram there is employed a known form of liquidoperated servo-mechanism adapted to control the fuel pump output, or athrottle valve, or a by-pass valve in the fuel supply system. In theexample shown, the servo-mechanism controls the output of a variabledelivery pump a of the swash plate type, the said mechanism serving tovary the Obliquity of an adjustable swash plate b. The servo-mechanismcomprises a cylinder c containing a spring loaded piston d. Both ends ofthe cylinder are in communication through a restricted orice e, andpressure uid is admitted to one end of the cylinder at f. An outlet g atthe other end of the cylinder is controlled by a valve h operable by alever i. The arrangement is such that when the valve is closed thespring y moves the piston in the direction for increasing the rate offuel supply to the burner 1c in the combustion chamber of the primemover, and when the valve is opened the pressure of the liquid moves thepiston in the direction for reducing the rate of fuel supply.

In association with the said valve lever 11 there is provided inaccordance with the present invention, a cylinder m containing a pistonn which is loaded by a suitable spring o, the end of the spring remotefrom the piston being supported 1 Claim. (Cl. 15S-36.3)

by one side of the lever. The end of the cylinder adjacent to the leveris divided by a diaphragm p to form an antechamber w, the diaphragmbeing of smaller effective diameter than the piston. Instead of adiaphragm an equivalent piston may be used. This diaphragm (or piston)acts on the other side of the lever.

In series with the fuel supply pipe q there may be provided if desired aspring loaded valve 1' cooperating with a seating s, and such that theextent of opening of the valve depends on the difference of pressure inthe liquid fuel between the entrance and exit sides of the valve. Theapproach side of the valve r is connected by a pipe t and a restrictedorice u to the end of the cylinder m containing the piston nl, and isalso connected to the antechamber w by a pipe o. The intermediate partof the cylinder containing the spring is, in this example, connected tothe discharge side of the valve 1. 'Ihe valve r is, however, notessential, and may be replaced by a restrictive orifice of fixeddiameter. Alternatively neither of these devices may be necessary insome cases, the pipe q being then connected directly to the burner 7c,and the intermediate part of the cylinder m being then connected to asump or the inlet side of the fuel pump.

The arrangement is such that in the event of an increase of pressure inthe pipe q due to an increase in the rate of ow in the said pipe,following a sudden opening of the drivers throttle valve 1L, a temporarypressure difference will result across the restricted orice u, and whenthe pressures which consequently act on the mechanism above describedare such that the force exerted on the valve lever z' by the diaphragm p(or piston) is greater than that exerted on the piston n, the lever willbe moved in the direction for causing the servo-mechanism to reduce thefuel. And When the pressure difference is subsequently reduced, themechanism resumes its previous condition. Spillage through the valve hmay be returned to a sump, or to the inlet side of the pump, by way of apipe y.

It will be understood that the action above described is only atemporary one, and its effect is to obviate an undesirable suddenincrease of rate of fuel supply, with risk of temporary overfueling ofthe prime mover, when the drivers throttle valve is opened suddenly. Inother words the effect is to make the rate of increase of fuel supplyindependent of the rate at which the driver actuates the throttle valveunder his direct control when he desires to accelerate the prime mover.

The invention is not, however, restricted to the 3 example abovedescribed. Thus the restricted orice u and the connection with theantechamber w may be arranged in any part of the fuel supply system inwhich an appropriate change of pressure accompanies a change in the rateof now. Moreover, and as already stated, the servomechanism may beadapted to actuate any other means than the pump control means forvarying the rate of supply of fuel to the burner lc. Also the part abovedescribed as the throttle :c may be any other manually controllablemeans for varying the rate of supply of fuel to the burner.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

A liquid fuel supply system comprising in oombination a liquid fuelpump, at least one liquid fuel burner, means connected to and providinga passageway between the discharge side of said pump and said burner, athrottle in said passageway, a liquid-operated servo-mechanism forcontrolling the rate of fuel flow from said pump to said passageway, avalve controlling said servomechanism and having an actuating lever, acylinder, a piston slidable in said cylinder, a spring arranged betweensaid piston and one side of said lever, a pressure responsive member ofsmaller eective area than said piston acting on so that said actuatinglever is movable in one direction through the medium of said pressureresponsive member by said liquid pressure difference, and is thereaftermoved in the opposite direction through the medium of said `piston andspring as said liquid pressure difference is reduced.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 2,474,033 Chamberlin et al. June 21, 1949 2,523,214 IfleldSept. 19, 1950 2,536,556 Lawrence Jan. 2, 1951 2,537,631 Lawrence Jan.9, 1951 2,562,615 Huber July 31, 1951 2,564,263 Ifleld Aug. 14, 19512,605,709 Jubb Aug. 5, 1952

